There are two basic styles in crib mattresses: spring or foam. Steel spring mattresses are slightly more popular in the United States, but both springs and foam can be good options. They do, however, have different features you need to watch for.

Spring Mattresses

There are a few things to watch for in a spring mattress: the quality of the materials (especially the insulation pad), the gauge of steel used in the coils, and how many coils are in the mattress. Fortunately, all that information should be included in a tag on the side of the mattress. If you’re buying online, the manufacturer should disclose their product’s materials. Check this list against the list printed on the mattress tag, and return it if they don’t match exactly. When it comes to crib mattresses, don’t buy it if you can’t tell exactly what materials were used.

Steel can come in gauges from 12-19. Lower gauge steel is thicker. Ideally, look for a mattress that uses 15 gauge or lower. The number of coils affects how the mattress feels and distributes weight, as well as its firmness. A higher number of coils won’t necessarily compensate for higher gauge steel, however. Mattresses in the 125-175 coil range are usually a good bet, especially with low gauge steel coils.

The insulation pad is the layer that protects you from the coils in the mattress. Coir Fiber, made from coconut hulls, is the strongest option for this layer. Avoid fiber-wrap insulation pads, also called rag wrap, as the fabric isn’t as strong. If the insulation pad is made of woven polyester, the weakest version, the mattress should immediately been taken off your list. Not only can woven polyester wear out, but it’s also prone to forming pockets where there isn’t any protection.

You should also look for border rods. These steel rods in the edges and corners prevent the edges of the mattress from collapsing when your child stands up or crawls to the edge of the mattress. These are an important safety feature, so you shouldn’t consider any spring mattresses without them.

Foam Mattresses

These mattresses are just as durable as spring versions, but they don’t have as many components, so you don’t have to check as many details. There are really two qualities you need in a foam mattress: firmness and density.

Firmness we’ve already talked about, but density will help the foam last longer without malformation or creating a bowl where your child sleeps. A good way to test density beyond what the mattress tells you on the label is to pick up the mattress and press your hands into the same place on both sides. A good mattress won’t let you compress it much and will spring back to shape quickly.